Printronix 108525-001, Maintenance Manual

Page: 55 / 456

2-35 P6040/P6080 Principles of Operation
2-6. Logic C3 PCBA
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continued
Table 2-9. Logic C3 I/O Address Map
-continued
Address (A23-A0) Function Comments
04011C
040140
040142
040144
NHMRBLK RES
NHMRBLK SET
MCHACK RES
MCHACK SET
Hammer Blank
Hammer Blank
Char Acknowledge
Char Acknowledge
040146
040148
04014A
04014C
04014E
040150
040152
040154
040156
040158
04015A
04015C
04015E
ONL RESET
ONL SET
BUSY RESET
BUSY SET
RDY RESET
RDY SET
REVCHNL RES
REVCHNL SET
IBSYRST RES
IBSYRST SET
OPS RESET
OPS SET
FBSYEN RES
FBSYEN SET
04011E
Online Control
Online Control
Busy Control
Busy Control
Ready Control
Ready Control
Reverse Channel Control
Reverse Channel Control
Busy Reset Control
Busy Reset Control
Output Polarity Control
Output Polarity Control
Fast Busy Enable Control
Fast Busy Enable Control
w. Memory Circuits
Three different memories are used on the logic C3. EEPROM for the system setup parameters,
EPROM for program and FONT data, and DRAM for the dot image buffer and other temporarily
stored data.
x. EEPROM
The EEPROM, residing on the lower data bus, stores all the setup/restore values for the printer.
The addressing of the EEPROM starts from 050000 and extends to 05FFFF. Presently, a 512 x 8
device is called out, but larger devices (2K x 8) are available if required. The 512 bytes are mapped
on top of each other throughout the 50000 to 5FFFF address space. This means that any one if 128
different addresses between 050000 and 05FFFF can access the same byte within the EEPROM.
This is due to incomplete address decoding. A memory disable circuit inhibits writes to the
EEPROM if the +5V supply goes below 3.3V. The EEPROM is located at 14G on the logic C3.
y. EPROM
The logic C3 card has sockets for 10 EPROM devices. Devices that will work in the sockets include
2764, 27128 and 27256 (with BA15 jumpers installed). The addresses where the EPROMs can be
accessed are defined in Table 2-8. Locations for the EPROMs are: EPROM0 (7G, low byte, 7J
high byte), EPROM1 (8G low byte, 8J high byte), EPROM2 (10G low byte, 10J high byte),
FONTO (11G low byte, 11J high byte) and FONT1 (12G low byte, 12J high byte). The high and low
byte EPROMs must be placed at each memory decode for the required word (16-bit) wide data
path. The EPROM0 proms must be in place in order to run any program. EPROMs are only accesĆ
sible from the processor or the expansion interface.
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